The present invention relates to a precision type torque limiting wrench which has a marking mechanism to mark a part that is tightened by the wrench at the instant the intended torque has been applied to the part.
A torque limiting wrench has application in various environments, including automotive, aircraft, and related production lines, where it is desired to apply an equal torque value to each of a number of parts or fasteners. In such environments, the intent is that there is no perceptible variation in the torque to which each part or fastener is finally taken, thereby avoiding localized stressing of secured members.
In the use of torque limiting wrenches in mass production and assembly, it is also desirable that an inspector have a means for quickly assuring himself visually that each and every fastener has received the desired torque application, and that all of the fasteners have been identically tightened. Thus, a motion-responsive marking device has been typically incorporated into the torque limiting wrench to make this possible with ease.
The patents to Woods, U.S. Pat. Nos. 2,274,638; 2,897,704; and 3,016,773, all show torque limiting wrenches of the general type involved in the present tool, but lacking marking means of any sort. The patents to Lance, U.S. Pat. Nos. 3,523,471; 3,662,629; and 3,667,327, assigned to the assignee of the present invention, deal with part marking means incorporated in a torque wrench, but include marking mechanisms of a relatively complex and expensive nature, as compared with the simplicity, compactness and low production costs of the direct acting marker means of the present invention.
One of the problems with known torque wrench constructions is that there has been no convenient way of replacing the part engaging head assembly of the wrench with another head assembly of a different size. This, of course, is desirable when the wrench is used on parts or fasteners of various sizes. It is conventional in torque limiting wrenches of the type shown in the above-mentioned patents to directly connect the part engaging head assembly and associated marking mechanism to the pivotal torque applying arm of the wrench. When it becomes necessary to change one head assembly for another, a relatively complex uncoupling and recoupling procedure must be followed involving several parts, therby making the changeover time-consuming and expensive. Thus, there has been a need for a torque limiting and marking wrench having a quickly releasable part engaging head assembly that may be removed and replaced without affecting or involving the marking mechanism or torque applying arm of the wrench.
Another problem associated with known torque and marking wrench constructions is their inability to be changed in configuration when the working space available changes or when the position of the part or fastener changes. As the operator moves from one part to another, the position of the part may change and the working space available may change as well. Thus, another aspect of the present invention resides in providing a torque limiting and marking wrench that is adaptable to be configured in various positions depending upon the location and attitude of the part and the available work space.